Fatigue, one of the most common material degradation mechanisms in industry in general and in the bearing industry in particular, occurs when material experiences lengthy periods under repeated or cyclic stresses which can lead to failure at stress levels much lower than the tensile or yield strength. It has long been recognised that nearly 90% of industrial component failure takes place due to fatigue. Hence the importance of evaluation of fatigue damage in metallic components and building a solid understanding of the fatigue phenomenon, aiming at preventing fatigue failures from occurring.
One example in this direction is EP1184813A2. EP1184813A2 describes how a dynamic equivalent load P is calculated from data information of a rolling bearing. Thereafter, a reliability coefficient aI is determined, a lubrication parameter aL corresponding to a used lubricant is calculated, and a contamination degree coefficient ac is determined in consideration of a material coefficient. A fatigue limit load Pu is calculated on the basis of the data information. Thereafter, a load parameter {(P−Pu)/C}·1/ao is calculated. On the basis of the lubrication parameter and the load parameter {(P−Pu)/C}·1/ao, a life correction coefficient aNSK is calculated with reference to a life correction coefficient calculation map. The bearing life LA is calculated as LA=aI·aNSK·(C/P)P.
Unfortunately life models commonly approach the fatigue problem in a simplified manner and commonly treat the metal in a highly idealised way. The models therefore exhibit limitations and there seems still to be room for improvements as regards the understanding of the characteristics of metals, especially as a bearing material, the life models, and the influences from the operating environment on the characteristics of bearing material.